A communication device capable of performing radio communication between a control substrate housed in a case and a device disposed outside the case is known As a conventional technique relating to such a communication device, there is a technique disclosed in Patent Literature 1.
The communication device such as that shown in Patent Literature 1 is assumed to be used in a dangerous area The dangerous area is a place in a general factory, where that is a risk that explosive gas could mix with air and generate a dangerous atmosphere having a lower explosion limit or more A communication device assumed to be used in the dangerous area is required to comply with intrinsically safe explosion-proof requirements (JIS C60079).
The communication device is configured to be such that a control substrate and a sub-substrate connected to the control substrate via a connector are housed in a metal case This is because, in order to suppress an increase in size of the communication device, a configuration which is provided with a sub-substrate for performing communication in addition to a control substrate and which connects both substrates by a connector is desirable An opening is formed in the case for performing communication, and a window member faces this opening.
Meanwhile, the communication device used in a dangerous area is restricted in electric power and capacity (inductance and capacitance) so as to comply with intrinsically safe explosion-proof requirements, and it is necessary to further limit the capacity when the electric power increases with an increase in a size of an electronic circuit Therefore, in order to alleviate the limit on the capacity, it may be desirable to design the electronic circuit so as to be regarded as a plurality of areas different from each other in terms of the intrinsically safe explosion-proof requirements However, a fact that a special design and an increase in a size of the connector are accompanied in order for the electronic circuit to be regarded as the plurality of areas is undesirable in terms of a manufacturing cost and a mounting space of an electronic component It is desired to achieve both separation of electronic circuit areas and use of a general-purpose connector in a communication device in which an electronic circuit is composed of a control substrate and a sub-substrate.